Ethylene vinyl acetate compositions and film and methods related thereto

ABSTRACT

The present invention relates to film-forming compositions containing ethylene vinyl acetate copolymers with a vinyl acetate percentage that causes film-forming problems and processability problems and an alkylene bisoleamide which is used to enhance the film forming capabilities of theses high VA content resins. The invention also relates to films prepared from theses compositions and to coating compositions.

This application claims the benefit of No. 60/028,063 filed Oct. 4,1996.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to certain polymeric blends containingolefinic bisoleamides such as EBO (N,N-ethyleneBisOleamide) and ethylenecopolymers such as ethylene vinyl acetate (EVA). The compositionprovides enhanced film forming properties in the production of monolayeror multilayer film products.

2. Description of Related Art

Ethylene vinyl acetate copolymers (EVA) are known and have a widevariety of applications in the industrial arts. EVA copolymers findcommercial use in flexible, heat sealable, functional, and decorativehot-melt and solvent-applied coatings; as wax additives to imparttoughness, flexibility, and adhesion; as blending resins to impartflexibility to brittle materials; and as a component of hot-melt andsolvent-applied adhesives. It is also known that the vinyl acetatepercentage in these copolymers can be varied and many such resins aresold under the trademark ELVAX® by E. I. du Pont de Nemours and Company.The present inventors have found that the film forming properties andprocessibility of this resin can vary with increasing vinyl acetatepercentage and that high vinyl acetate copolymers (e.g. greater thanabout 0% VA by weight) can cause film processing problems. In an effortto solve this problem for high VA content ethylene copolymers, theinventors have surprisingly found that the addition of EBO improves filmforming capability while minimizing negative effects on film propertiessuch as clarity or other required physical parameters.

U.S. Pat. No. 4,510,281 describes the combination of EVA copolymers withcertain oleamides to provide tack free pellets for industrial end uses.The oleamides and other esters described therein as additives improvethe free-flowing properties of the pellets by incorporating into thepolymer material prior to pelletization about 500-10,000 parts permillion (ppm), especially 1000-5000 ppm, based on the polymer weight ofan additive selected from the group consisting ofN,N′-ethylenebisoleamide, N,N′-ethylenebiserucamide,N,N′-diolelyladipamide, and N,N′-dierucyladipamide. There is no specificteaching in this reference of the use of the compositions therein toproduce a film or a film having processing advantages. There is,however, a general teaching relating to improvement of the handling andpackaging throughput in actual production as a way to monitor good slipproperties or antiblocking properties, especially for higher vinylacetate content copolymers which could not be assessed by standard sticktemperature tests. There is no requirement in the present invention thatthe additive be incorporated into the ethylene copolymer resin beforepelletization.

Grades of ELVAX® containing, for example, N,N-ethylenebisoleamide havebeen sold by E. I. du Pont de Nemours and Company for industrialapplications but have not been sold or used as packaging grade orfilm-forming resins. Grades of ELVAX® resins not containing an additiveof this nature have been sold into the packaging market.

U.S. Pat. No. 4,956,232 discloses the use of slip additives inmultilayer polypropylene films. Slip additives which may be used inmaking the films disclosed in the U.S. Pat. No. 4,956,232 patent arethose which are incompatible with polypropylene, i.e., those which bloomto the surface from the core and skin layers. Non-ionic surfactants,such as the amides and carboxylic acids, were of particularly interestin this patent disclosure. Amides which were preferred included amidesof carboxylic acids having at least five carbon atoms, for example,behenamide, linolenamide, arachidamide, ricinol-amide, palmitamide,myristamide, linoleamide, lauramide, capramide, perlargonamide,caprylamide, oleamide, steramide, N,N′-ethylene bisoleamide, and themost preferred slip additive, erucamide. Carboxylic acids which werealso described as useful included those having at least four carbonatoms, for example, butyric, caproic, caprylic, capric, lauric,lauroleic, myristic, myristoleic, pentadecanoic, palmitic, palmitoleic,margaric, stearic, oleic, linoleic, linolenic, ricinoleic,2,3-dihydroxystearic, 12-hydroxystearic, behenic, eleostearic,arachidic, 2-ecosenoic, 4-eicosadienoic, 2-docosenoic, 2-tetracosenoic,2,4,6-tetracosatrienoic and the like.

The slip additive in the above patent disclosure was preferably dryblended together with the polypropylene resin of layer (B) or theheat-sealable resin of layer (A) and then melt mixed. Alternatively, theadditive could be incorporated into a minor portion of the resin as amaster batch to form a high concentration mix of the additive and theresin. This could then be diluted to the appropriate proportion by theaddition of more resin. There is no teaching herein of the use of any ofthese additives with an EVA resin or film.

U.S. Pat. No. 4,517,242 discloses a combination of ethylene copolymerresins and lubricating agents such as ethylenebisoleamides in glasscoating compositions.

U.S. Pat. No. 3,879,330 discloses food wrap consisting of a vinylidenechloride polymer and a thermoplastic urethane polymer. The food wrapfilms of the invention can contain conventional additives such aslubricating additives, anti-blocking agents, anti-cling agents, and thelike, all of which are known in the art. To illustrate, the food wrapfilms of the invention typically contain up to about 3 weight percentdiatomaceous earth as an anti-blocking agent and up to about 2 weightpercent of ethylenebisoleamide as a slip agent.

U.S. Pat. No. 5,468,444, describes the production of orientedthermoplastic films by blown-film extrusion. U.S. Pat. No. 5,453,209discloses chemical metal and oil treating compositions and processesrelated thereto. U.S. Pat. No. 4,394,473 discloses polybutadiene bagsand films. U.S. Pat. No. 3,645,822 discloses a method for providingmultilayer films having improved slip properties. U.S. Pat. No.5,468,444 discloses film-forming thermoplastic resins containinglubricants selected from aliphatic alcohol fatty acid esters obtainedfrom an aliphatic alcohol having 1 to 12 carbon atoms, and preferably 1to 6 carbon atoms, and a fatty acid having 10 to 22 carbon atoms, andpreferably 12 to 18 carbon atoms, such as glycerol monooleate, glyceroldi- or trioleate, glycerol triricinoleate, glycerol acetylricinoleate,methyl acetylricinoleate, ethyl acetylricinoleate, butylacetylricinoleate, propylene glycol oleate, propylene glycol laurate,pentaerythritol oleate, polyethylene glycol oleate, polypropylene glycololeate, polyoxyethylene glycerol, polyoxypropylene glycerol, sorbitanoleate, sorbitan laurate, polyethylene glycol sorbitan oleate, andpolyethylene glycol sorbitan laurate; polyalkylene ether polyols, suchas polyethylene glycol and polypropylene glycol; sugar fatty acidesters, epoxidized soybean oil, polyoxyethylene alkylamine fatty acidesters, polyoxyethylene alkylphenyl ethers; higher fatty acid amideshaving 12 to 22 carbon atoms, such as oleamide, stearamide, anderucamide; ethylene-bis-stearamide, ethylene-bisoleamide, polyethylenewax, polypropylene wax, and liquid paraffin. Suitable nucleating agentsinclude inorganic substances, such as talc and silica. Suitabletackifiers include castor oil derivatives, low-molecular viscouspolybutylene, sorbitan higher fatty acid esters, terpene resins, andpetroleum resin.

BRIEF SUMMARY OF THE INVENTION

The present invention relates to a polymeric film forming compositioncomprising an ethylene copolymer selected from an ethylene copolymer andan olefinic bisoleamide selected from an oleamide which affectsfilm-forming properties of high ester content ethylene copolymer resinswhich heretofore have not produced film with the requisite physicalproperties. The present invention relates to a film-forming compositionconsisting essentially of an ethylene copolymer having a percentage ofvinyl acetate monomer incorporated at 10% wt or higher relative to theethylene, and an olefinic bisoleamide of the formula described hereinwherein the oleamide additive is not required to be added to thecomposition prior to pelletization of the ethylene copolymer. Thepercentage of bisoleamide necessary to have the beneficial physicalproperties varies with the percentage of vinyl acetate in the film orextrusion coating and depends upon the thickness of the film or coating.Upon reading this disclosure, one of ordinary skill in the art canreadily adjust the percentages accordingly.

The present invention also relates to a coating composition forextrusion coating comprising an ethylene copolymer having ethylene andan ester containing monomer (e.g. vinyl acetate or C1-C6 alkyl acrylateesters) and a bisoleamide of the formula described herein wherein theoleamide is not added to the composition prior to pelletization. Thebisoleamide may be added post-pelletization and pre-extrusion.

The present invention also comprises a film having a first layer whereinthe layer contains a polymeric composition comprising an ethylenecopolymer selected from a copolymer of ethylene and a vinyl esterincluding vinyl acetate and an olefinic bisoleamide selected from acompound of the formula R—C(O)—NHC₂H₄NHC(O)—R wherein R is selected froma C₄-C₂₅ saturated or unsaturated hydrocarbon. The invention alsocomprises a film having a first layer which contains a polymericcomposition comprising an ethylene copolymer selected from a copolymerof ethylene and a vinyl ester including vinyl acetate and an olefinicbisoleamide selected from a compound of the formulaR—C(O)—NHC₂H₄NHC(O)—R wherein R is selected from a C₄-C₂₅ saturated orunsaturated hydrocarbon and a second layer comprising an ethylene acidionomer selected from copolymers of ethylene and acrylic acid ormethacrylic acid which are neutralized with a metal hydroxide or saltwherein the metal includes sodium, magnesium, calcium, etc. Suchionomers are sold under the trademark SURLYN® by E. I. du Pont deNemours and Company. Any of the film or coating layers may also containblends of, for example, polyethylene including linear low densitypolyethylene or ultra low density polyethylene. The relative percentagesof the blends depends upon the operator's target parameters and economicor other considerations.

The present invention further relates to a method of enhancing the slipcharacteristics of ethylene vinyl acetate films comprising adding anadditive selected from an olefinic bisoleamide of the formulaR—C(O)—NHC₂H₄NHC(O)—R wherein R is selected from a C₄-C₂₅ saturated orunsaturated hydrocarbon to an ethylene vinyl acetate copolymer andproducing the film. In particular, the bisoleamide permits effectiveslitting of blown film having a high percentage of vinyl acetate orother ester functionality wherein said film, absent the bisoleamide,would adhere or otherwise stick together to preclude or preventeffective slitting of the two-layer structure coming out of theblown-film pinch rollers. The invention also relates to a process formaking a film comprising, (a) blending an olefinic bisoleamide selectedfrom an olefinic bisoleamide of the formula R—C(O)—NHC₂H₄NHC(O)—Rwherein R is selected from a C₄-C₂₅ saturated or unsaturated hydrocarbonwith an ethylene copolymer selected from copolymers having ethylene andan ester containing monomer including vinyl acetate to form a blend and(b) forming a film or extrusion coating from the blend having at leastone layer.

The present invention improves the separation of film layers in blownfilm, both in the separation of the film “layflat” after the blown filmstalk is pressed together or nipped which collapses the hollow filmstalk upon itself or in subsequent separation of the layers of film on afilm roll. In the former separation, the cylindrical hollow film stalksuch as from a spiral blown film die, is flattened and collapsed betweentwo moving nip rolls which flatten and press the cylindrical hollow filmstalk into a two layer “layflat” sandwich. This film tube is cut at theedges and separated into two film layers, each of which are rolled ontoa core forming rolls of film. The layflat is difficult to separate intothe separate film layers, especially as the vinyl acetate monomerconcentration increases in the ethylene copolymer resin that the film ismade from. In the latter case of film layers on a roll, layers of filmwhich have been wound onto a core or roll may be difficult to separatesince the layers tend to stick together, again especially as the vinylacetate monomer concentration increases in the ethylene copolymer resinthat the film is made from. In both cases, the N,N′-ethylenebisoleamidesurface effects of reducing tackiness and improving film slip(increasing) properties occurs fast enough to allow separation of thefilm layers and therefore successful operation of these type processes.

The present invention also improves film cutting or slitting in filmfabrication processes. The surface effects of theN,N′-ethylenebisoleamide on the film occurs fast enough so that filmcutting is often improved. Without the olefinic bisoleamide, the devicewhich cuts the film such as a sharp razor, often catches on the film dueto its tacky nature and poor slip qualities and results in the filmjumping off the cutter or stretching of the film. Due to the quickaction of reducing film tackiness and improving slip properties, in linefilm cutting is significantly improved with less drag forces between thecutting device and the film.

DETAILED DESCRIPTION

As summarized above, the present invention relates to ethylenecopolymeric film-forming compositions containing an additive selectedfrom an olefinic bisoleamide. The additive surprisingly providesenhanced film forming properties to an ethylene copolymer having apercentage of vinyl acetate monomer incorporated at 10 wt % or higherwithout impacting in a negative manner other film parameters such asclarity.

It has now been discovered that the film-forming and processingproperties of polymers selected from the group consisting of

(a) copolymers of ethylene with an ester containing monomer such asvinyl acetate containing about 10-40 weight percent of vinyl acetate orester containing monomer, or

(b) terpolymers of ethylene with vinyl acetate and carbon monoxidecontaining about 20-40 weight percent of vinyl acetate and 3-12 weightpercent of carbon monoxide can be significantly improved byincorporating into the polymer material about 500-10,000 parts permillion (ppm), especially 500-5000 ppm, based on the polymer weight ofan additive selected from the group consisting ofN,N′-ethylenebisoleamide, N,N′-ethylenebiserucamide,N,N′-diolelyladipamide, and N,N′-dierucyladipamide. For the purpose ofthis invention (the term “oleyl” means cis-9-octadecenyl,C₈H₁₇CH═CH(CH₂)₇CH₂—; and the term “erucyl” means cis-13-docosenyl,CH₈H₁₇CH═CH(CH₂)₁₁CH₂—. This nomenclature is generally used in thetrade, for example, for oleyl alcohol, oleylamine, and erucylamine.

Polymeric Film Forming Compositions

Ethylene Copolymers

The ethylene copolymers of the present invention are selected from

(a) copolymers of ethylene with vinyl acetate containing about 10-40weight percent of vinyl acetate, or

(b) terpolymers of ethylene with vinyl acetate and carbon monoxidecontaining about 20-40 weight percent of vinyl acetate and 3-12 weightpercent of carbon monoxide. These copolymers are generally availableunder the trade names ELVAX® or ELVALOY® as sold by E. I. du Pont deNemours and Company and are generally prepared from ethylene and variouspercentages of vinyl acetate and, if necessary, carbon monoxide; or

(c) copolymers of ethylene with ester containing monomers selected frommethyl acrylate, butyl acrylate, isobutyl acrylate or terpolymerscontaining carbon monoxide.

The preferred ethylene copolymers are selected from ethylene vinylacetate copolymers having a vinyl acetate percentage by weight relativeto the ethylene in the range of 15-40 wt. % The most preferred ethylenevinyl acetate copolymer utilized in the film forming composition isselected from 15-33 wt. % or as exemplified herein.

For the purpose of this invention, the term “vinyl acetate copolymer”includes both the dipolymers and the terpolymers of ethylene with vinylacetate and with carbon monoxide. Most commercial EVA dipolymers containabout 2-55% by weight of vinyl acetate. Terpolymers of ethylene withvinyl acetate and with carbon monoxide may contain about 18-40 weightpercent of vinyl acetate and 2-12 weight percent of carbon monoxide.Dipolymers of ethylene with vinyl acetate are available, e.g., from E.I. du Pont de Nemours and Company, Wilmington, Del., under the.trademark Elvax®; the terpolymers with carbon monoxide can be madeaccording to the teachings of U.S. Pat. No. 2,495,286 to Brubaker andU.S. Pat. No. 3,780,140 to Hammer. As the vinyl acetate content of thecopolymer increases, the copolymer tends to become increasingly stickyin both film and pellet states.

As discussed above, while use of the bisoleamides for antiblockingpurposes is known, however, high VA content EVA copolymers are generallynot used to produce film. The present inventors have discovered that theEVA copolymers with between 10-40% VA content can produce film with goodproperties provided that an olefinic bisoleamide is present in thecomposition as a primary additive.

Primary Additives

The olefinic bisoleamides are generally selected from a compound of theformula: R—C(O)—NHCH₂CH₂NHC(O)—R wherein R is selected from C₄-C₂₅saturated or unsaturated hydrocarbon moieties. In particular, theolefinic bisoleamides are selected from the group consisting ofN,N′-ethylenebisoleamide, N,N′-ethylenebiserucamide,N,N′-diolelyladipamide, and N,N′-dierucyladipamide. The amides of thisinvention can be added to the copolymers by any convenient technique,for example, in the melt, as a dry powder below its melting temperature,or as a concentrate in the same or any compatible polymer. The additiveis thoroughly blended with the polymer, which is then used to produce(via extrusion) the film or coating of the present invention.

The preferred olefinic bisoleamide is selected fromN,N-ethyleneBisOleamide (EBO). N,N′-Ethylenebisoleamide is availablecommercially from Carstab Corp. in Reading, Ohio, under the name“Advawax” 240; from Humko Sheffield Co., Memphis, Tenn., under the name“Kemamide” W-20; and from Glyco Chemical Co., Greenwich, Conn. under thename “Glycolube” VL. The commercial product has a melting range of113°-118° C. It is recommended by its manufacturers as processinglubricant and antiblocking agent for various polymers and copolymers,especially as a slip agent for films. Its recommended level for theseuses is 0.5-2%. As discussed above, however, there is no recommended useknown for processing this additive with high VA content resins for film.The other additives can be made by known methods from readily availablematerials. Thus, N,N′-ethylenebiserucamide is made by heating1,2-ethylenediamine with erucic acid, and the remaining two amides aremade by beating either adipic acid or its dimethyl ester with at leasttwo equivalents of either oleylamine or erucylamine. The adipamide thushas the formula RNH—C(O)—(CH₂)₄—C(O)—NHR where R is either the oleyl orthe erucyl group.

The relative weight percentage of olefinic bisoleamide to the ethylenecopolymer ranges from 200-10,000 ppm. As indicated above, the percentageof bisoleamide will vary depending upon other parameters including VAcontent and thickness of the film or coating. In an 18 wt. % VA film,1,000-3,000 ppm is the preferred range. In a 12 wt. % VA film, 700 ppmprovides good slitting properties.

Additional Excipients

Additional excipients which are normally added to film forming orextrusion coating compositions include antiblock agents, fillers andother excipients known to those of ordinary skill in the art. As statedabove, these additional ingredients can include other polymers, etc.,including polyethylenes or ethylene copolymer ionomers such as thoseionomers sold under the trademark SURLYN® by E. I. DuPont de Nemours andCompany in additional or adjacent layers.

The film forming composition is prepared by mixing the olefinicbisoleamide with the ethylene copolymer as described below in a blownfilm forming process.

Film

Blown Film Forming Process

The vinyl acetate and ethylene copolymer resin, either containing theN,N′-ethylene bis oleamide or mixed with pellets containing theN,N′ethylene bis oleamide component, is conveyed to the feedthroat of anextruder. The extruder heats the resin particles, melts them andplasticates the copolymer into a blended melt and then pumps this meltedcopolymer material into a spiral die. The molten polymer is then pulledand formed into a circumferential hollow thin film stalk around anenclosed gas pocket or gas pressurized volume. The cooling of the moltenpolymer film which occurs just exit of the circular thin slit dieopening and in drawing it over this enclosed gas volume providessufficient strength to the polymer mass to pull and form or draw ahollow thin film stalk. This cylindrical thin film with the enclosed gasvolume is at some point, collapsed between two counter rotating rollspressing the cylindrical film together forming a two layer sandwichreferred to as a layflat. The layflat is typically cut or slit on itsedges forming 2 plies of film which are still layered together. The 2film plies of the layflat are usually separated into individual filmsand rolled onto a turning core forming a roll of film. (This inventionallows improved cutting and separation of the 2 film layer layflat forEVA films with VA levels of 1040%—due to its fast bloom and fast surfaceenhancing effects of reducing tackiness, sticking and COF (coefficientof friction).

Variants to this process include not slitting or separating the filmlayflat in the film forming process. If the circular die opening ishorizontal (versus vertical in typical “film blowing” processing), themolten polymer forming into a film is sometimes referred to as profileor tubing extrusion.

Coating Operations

The vinyl acetate and ethylene copolymer resin, either containing theN,N′ethylene bis oleamide or mixed with pellets containing theN,N′ethylene bis oleamide component, is conveyed to the feedthroat of anextruder. The extruder heats the resin particles, melts them andplasticates the copolymer into a blended melt and then pumps this meltedcopolymer material into a coating die. The coating die distributes themolten polymer uniformly to a thin straight slit opening. Molten polymerflowing from the thin straight slit die forms a curtain or web which cancoat a substrate moving beneath the slit opening. Just after the webcontacts the moving substrate, the molten polymer is cooled by nipping,pressing or contacting the coating against a cool roll. The coatedsubstrate is usually cut to a desired width and rolled onto a core. Withhigher VA EVA copolymer coating resins, the coating can stick to thecooling roll just after the molten polymer is dropped onto the movingsubstrate resulting in processing problems such as tearing the substrateand wrapping around the cooling roll. This invention facilitates usinghigher VA EVA copolymers due to the faster blooming effect of the slipand enhanced release properties that occur in the short time span priorto contacting the cooling roll.

EXAMPLES

The following examples provide exemplary support for the claimedinvention and should not be construed as limiting the claimed subjectmatter. The examples below clearly demonstrate that the olefinicadditive and resultant ethylene copolymeric composition has good filmforming and processing properties even at significant vinyl acetatepercentages (e.g. greater than about 10% and preferably greater thanabout 18%) and the additive greatly enhances the slip characteristics ofethylene vinyl acetate films which makes these films easier to handleand process and allows the film to run faster on film forming equipment.As demonstrated below, the films containing the olefinic additive and,for example, EVA can be made as single layer or a multilayer films(coextruded or laminated).

Example 1

A coextrusion was conducted of mostly two-layer films of SURLYN® 8240, a2.8 MI sodium ionomer having a melting point of 90° C., a productavailable from DuPont and a blend of ELVAX® 3182, a 3 MI ethylene-vinylacetate resin having a vinyl acetate content of 28 wt. %, and XEP 23.XEP 23 is a concentrate composed of 95 wt. % of ELVAX® 3182, 2 wt. %N,N′-ethylene-bis-oleamide (#5), and 3 wt. % silica (in the form ofdiatomaceous earth). The EVA resin layer was made up of 75 wt. % of the3182 resin and 25 wt. % of the XEP 23 resin. The use level of theN,N′-ethylene-bis-oleamide was thus 0.5 wt. % or 5,000 ppm of theadditive in the resin, and the amount of silica was 7,500 ppm.

These coextrusions were carried out on a 2.5″ (63.5 mm) WELEX blown filmextrusion line extruding the EVA layer, and a 1.5″ (38.1 mm) Davisextruder was used for the ionomer layer. The thickness of the EVAcontaining layer may range from 0.8 mil to 8 mil (0.2-2 mm). Thetemperature profiles for the two extruders were as shown below:

Ex- Ctr. truder Rear Rear Center Ctr. Frt. Front Head Adap. Die Welex300 350 375 380 380 380 380 380 Davis 375 390 390 390 380 380 380 380

The films produced ranged in total thickness between 4.02 and 5.07 mils(1-1.25 mm), and the percentages of the outside ionomer layer thicknessranged from 19.6 to 48.6% of the total. All of the samples were preparedat a blow-up ratio of approximately 1.75:1 using an 810″ diameterGloucester die. The film take-off rate ranged from 15 to 47 feet/min(4.6-14.3 met/min). Chilled air of approximately 50° F. (10° C.)temperature was fed to the air ring at a rate of 30 to 59 cu. ft./min(0.85-1.7 cu m/min). The tubular film from these extrusions could bereadily opened by the time it reached the slitter-rewinder.

Example 2

A concentrate was made containing 5.0 wt. % N,N′-ethylene-bis-oleamide#5, 7.5 wt. % “Superfloss” silica, with the remainder being the carrierresin ELVAX® 3182 to form “VAX CE9746”. The concentration of theadditives was selected so that 10 wt. % of the concentrate could toadded to 90 wt. % of the EVA resin, the additive concentrations being2.5× of those in XEP 23 in Example 1 above. Three coextruded films wereproduced from the compositions described below. Number 1 film was 1.2mils (0.03 mm) ionomer recipe outside and 4.8 mils (0.12 mm) EVA recipeinside. Number 2 film was 2.5 mils (0.06 mm) ionomer recipe outside and2.5 mils (0.06 mm) EVA recipe inside. Number 3 film was 2.5 mils (0.06mm) ionomer Recipe outside and 2.5 mils (0.06 mm) ionomer recipe inside(COMPARATIVE).

The composition of the ionomer recipe used for the above layers was:

93 wt. % SURLYN® 8240; 2.0 wt. % CONPOL 13B (12.5 wt. % “Superfloss”Silica in 9 wt. % methacrylic acid (MAA)-content EMAA resin, 10 MI;antiblock concentrate); and 5 wt. % “Ampacet” 11200 (Commercial WhiteConcentrate of 70 wt. % TiO2 in ethylene-methyl acrylate copolymercarrier).

The composition of the EVA formulation used in the three films was:

85.5 wt. % ELVAX® 3182; 10.0 wt. % VAX CE9746 Slip/AntiblockConcentrate; and 4.5 wt. % “Ampacet” 11200 White Concentrate.

The two coextruded films having an outside layer of ionomer formulationand an inside layer of EVA formulation were successfully coextruded intogusseted film tubing. The face dimension of the tubing was 16.5″ inwidth (419 mm), and each gusset was 5.5″ (140 mm) deep. Samples of thetubing taken on arrival at the wind-up position of the film extrudercould be readily opened, showing the effectiveness of theN,N′-ethylene-bis-oleamide at the use level of 5,000 ppm. The EVA resinhas a much greater tendency to block and self-adhere, unlike the ionomerresin that requires only silica antiblock to give openability of thegusseted tubing.

Example 3

Five-layer film coextrusions were also conducted as described herein. AComparative concentrate additive composition and a concentrateformulation of the invention were prepared and compared for film-formingeffectiveness and capability. The five layer film comprised a centerlayer of a blend of 80 wt. % ethylene-vinyl alcohol copolymer and 20 wt.% of ELVAX® 3182. On each side of the center layer was a layer of anadhesive resin; and the outermost layers were composed of an ultralowdensity linear low density polyethylene (ULDPE) composition containingELVAX®, a color concentrate, and either a Comparative formulation (i.e.,without alkylene oleamide) or the film-forming composition of theinvention. The Comparative resin blend for the outermost layer was madeup of ULDPE29.27 (30 wt. %); ELVAX® 3182 (51.2%); SB#1 (a composition of20 wt. % silica, 3.5 wt. % stearamide, and 3.5 wt. % erucamide in acarrier resin of an 18 wt. % vinyl acetate content EVA resin having anMI of 2.5 g/10 min (ELVAX® 3170) which gave 19,000 ppm of silica in thelayer and 6,832 ppm of combined amides as slip additive); and colorconcentrate (9.8%).

The composition of the invention which includes the additive alkylenebisoleamides includes or consists essentially of SB#2 (a compositioncomprising 5 wt. % N,N′-ethylene bis oleamide, 7.5 wt. % “Superfloss”silica with the remainder being ELVAX® 3182). This concentrate waspresent in the outer layer formulation at 10 wt. %; color concentrate(7.5%); ELVAX® 3182 (52.5%); and ULDPE (30%). Thus the outer layerscontained 7,500 ppm silica and 5,000 ppm N,N′-ethylene bisoleamide.

The films were prepared using standard film processing and manufacturingtechniques for five layer films of this nature and under the sameextrusion conditions. The laid flat film tubing from the comparativefive layer film containing SB#1 could not be opened by the time itreached the wind-up. In contrast, the film tubing containing SB#2concentrate which actually had lesser amounts of both the silicaantiblock and the amide(s), could be opened readily.

The above examples demonstrate that the production of high VA contentEVA films can be accomplished without impairment of physical propertiesby incorporating an alkylene bisoleamide of the invention into thefilm-forming composition. This additive can also be added to anyethylene vinyl acetate copolymer resin grade used to produce film inplace of other slip additives and at lower concentrations. The enhancedmigration properties of the bisoleamides in and onto film surfaces alsoenhances slip properties. The film-forming enhancing additive of theinvention is particularly suitable for high VA content ethylene vinylacetate resins used to produce film which traditionally have highcoefficients of friction (COF); tackiness and blocking properties whichdiscourages the use of these resins in film production. The tacking andblocking tendencies are reduced by the addition of the recited additivewhich permits faster bloom rates and therefore improves and allows orenables film processing and production of these high VA contentcopolymeric resins. The inventors also noticed that use of the inventionreduced nip roll and winding blocking tendencies and improvedknife-razor performance in the conversion to film. Comparativeexperiments conducted at 18% VA and at 25% VA in an ethylene vinylacetate copolymer with similar weight loading of ADVAWAX 240(N,N′-ethylene bisoleamide) versus ecruamide showed that the formerexcipient enhanced film forming properties of the high VA copolymers andcompared more favorably to the comparative amide. Bubble stabilityincreased; razor slitting improved (smoother and cleaner); less problemoccurred in separating the web layflat-25%VA content EVA film withcomparative amide could not be separated while the run containingADVAWAX 240 could be separated. These favorable results occurred even at50% concentration levels relative to the amide.

What is claimed is:
 1. A film comprising at least two layers, including(1) a first layer consisting essentially of an ionomeric resin and (2) asecond layer consisting essentially of (a) an ethylene vinyl acetatecopolymer and (b) an alkylene bisoleamide of the formula:R—C(O)—NHC₂H₄NHC(O)—R wherein R is a C₄-C₂₅ saturated or unsaturatedhydrocarbon, and wherein the bisoleamide is present in an amount of fromabout 2000 to about 5000 ppm.
 2. The film of claim 1 wherein theethylene vinyl acetate layer has a vinyl acetate content of grater thanabout 10 wt %.
 3. The film of claim 2 wherein the ethylene vinyl acetatelayer has a vinyl acetate content of from about 10 wt % to about 40 wt%.
 4. The film of claim 3 wherein the ethylene vinyl acetate layer has avinyl acetate content of from about 15 wt % to about 40 wt %.
 5. Thefilm of claim 4 wherein the vinyl acetate layer has a vinyl acetatecontent of from about 15 wt % to about 33 wt %.
 6. The film of claim 5wherein the alkylene bisoleamide is selected from the group consistingof: N,N′-ethylenebisoleamide, N,N′-ethylenebiserucamide,N,N′-diolelyladipamide, and N,N′-dierucyladipamide.
 7. The film of claim6 wherein the alkylene bisoleamide is N,N′-ethylenebisoleamide.
 8. Aprocess for producing a multi-layer film of claim 1 comprising thesteps: (i) mixing an alkylene bisoleamide of claim 1 with an ethylenevinyl acetate (EVA) copolymer and (ii) co-extruding the blown filmobtained from the EVA copolymer/bisoleamide mixture with at least onelayer of an ionomeric resin to obtain the multi-layer film.
 9. A processfor producing a multi-layer film of claim 1 comprising the steps: (i)mixing an alkylene bisoleamide of claim 1 with an ethylene vinyl acetate(EVA) copolymer (ii) extruding the ethylene vinyl acetate/bisoleamidemixture (iii) blowing the extruded ethylene vinyl acetate mixture toobtain a blown film and (iv) laminating or coating the blown filmobtained from the EVA copolymer/bisoleamide mixture with at least onelayer of an ionomeric resin to obtain the multi-layer film.
 10. Theprocess of claim 9 wherein the ionomeric resin layer is coated onto theethylene vinyl acetate blown film layer.